1. Technical Field
The present invention relates in general to improvements in disk drive systems and in particular to swage connections for connecting head gimbal assemblies to actuator arms in a disk drive system.
2. Description of the Related Art
It has been a continuing objective of the disk drive industry to produce disk drive systems of increasing storage capacity, decreased size (or "form factor" as often used in the industry), and faster response time. One approach to increasing the storage capacity of a disk drive is to increase the number of disks. However, as the number of disks increases, the height of the disk drive also increases. To maintain the desired form factor of the disk drive, workers in the art are continually trying to reduce the spacing between disks.
While trying to reduce the spacing between disks, workers in the art are also trying to reduce the mass of the actuator and head gimbal assembly so as to decrease the response time of the disk drive. One way of reducing the mass of the head gimbal assembly is to bring the actuator hub closer to the center of the disk stack. This results in shorter, and thus lighter, head gimbal assemblies, and also in a disk drive having a smaller foot print.
Although one way to achieve the smallest possible spacing between the actuator hub and the center of the disk stack is for the actuator arms to fit between the disks, fitting the actuator arms between the disks limits the minimum spacing between disks since additional space must be left between the disks to allow for the actuator arm thickness and for the connection between the actuator arm and the head gimbal assembly. Therefore, in designing disk drives with form factors having a very small height, the actuator arms and swage connections are kept outside the disk stack to permit closer spacing of the disks. Workers in the art are continuously trying to bring the actuator hub as close as possible to the disk stack, while still keeping the actuator arms and swage connections outside the disk stack.
To bring the actuator hub as close as possible to the disk stack, while maintaining the actuator arms outside the disk stack, the actuator arms must be made as short as possible, and a suitable method of connecting the head gimbal assemblies to the actuator arms is needed. In the prior art, swage connections are often used to connect head gimbal assemblies to actuator arms. Swage connections are popular because they make assembly of the head gimbal assemblies onto the actuator arms particularly easy.
Prior art swage connections use a hole in the actuator arm and a boss on the member to be attached to the actuator arm. The boss is sized so that it fits inside the actuator arm hole. There is a boss hole through the boss, and a lip on the inside diameter of the boss hole. A hard ball is passed through the boss hole thus enlarging the boss and forcing the outside surface of the boss into the inside surface of the actuator arm hole. This swaging process causes the outside surface of the boss to "bite" into the inside surface of the actuator arm hole, thus causing the member to be fixedly connected to the actuator arm.
Both one-boss and multiple-boss swage connections are known in the art. However, prior art swage connections use a hole on the actuator arm that has material around 360 degrees of the hole. FIG. 7 shows a prior art actuator hub 122. Actuator hub 122 of FIG. 7 shows that the holes 161 in actuator arm 124 are completely surrounded by material, such as the material indicated by reference numerals 188.